Top 100+ Organisms and Populations - Biology Questions and Answers For NEET 2024 Exam Preparation

Q1. In growth pattern, (1 – N/K) is

1. intrinsic rate of natural increase
2. carrying capacity
3. environmental resistance
4. biotic potential

Answer: (c)

In growth pattern, environmental resistance (1 - N/ K) is the action of limiting abiotic and biotic factors that prohibit the growth of a population as it would grow according to its biotic potential.

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Q2. Two opposite forces operate in the growth and development of every population. One of them is related to the ability to reproduce at a given rate. The force opposite to it is called

1. fecundity
2. biotic control
3. environmental resistances
4. mortality

Answer: (c)

The environmental factors which can check the growth of population size constitute the environmental resistance. These include predators, food, water, nesting sites, similar competitors, etc. All living things tend to reproduce until the point at which their environment becomes a limiting factor. No population, human or otherwise, can grow indefinitely; eventually, some biotic or abiotic variable will begin to limit population growth.

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Q3. In laboratory experiments, two species of the protist Paramecium were grown alone and in the presence of the other species. The following graphs show growth of species 1 (left) and species 2 (right), both along and when in mixed culture. Interpretation of these graphs shows that

1. both species are affected by interspecific competition but species 1 is less affected.
2. competitive exclusion occurred in these experiments.
3. both species are affected by interspecific competition but species 2 is less affected.
4. both species are affected equally by interspecific competition.

Answer: (c)

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Q4. The integral form of equation (ii) as given in question 98 is __________

1. N = $N_0 e^{rt}$
2. N = $N_0 e^{rN}$
3. $N_t = N_0 e^{rN}$
4. $N_t = N_0 e^{rt}$

Answer: (d)

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Q5. The key elements which lead to much variation in the physical and chemical conditions of different habitat are enlisted below:

Temperature, Wind, Water, Light, Soil, Humidity, UV rays

1. 6
2. 5
3. 4
4. 3

Answer: (c)

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Q6. Which of the following is an incorrect statement?

1. The malarial parasite needs vector (mosquito to spread to other host).
2. The human liver fluke depends on two intermediate hosts to complete its life cycle.
3. Parasites that feed on external surface of the host organism are called endoparasites.
4. Cuscuta derives its nutrition from the host plant which it parasitises.

Answer: (c)

Parasites that feed on the external surface of the host organism are called ectoparasites. The most familiar examples of this group are the lice on humans and ticks on dogs.

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Q7. Benthic organisms are affected the most by

1. light reaching the forest floor
2. sediment characteristics of aquatic ecosystems
3. surface turbulence of water
4. water-holding capacity of soil

Answer: (b)

Benthic organisms are bottom dwelling forms found crawling or attached to the bottom. The sediment characteristics often determine the type of benthic animals that can thrive there.

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Q8. What will happen to a well growing herbaceous plant in the forest if it is transplanted outside the forest in a park?

1. It will grow well because it is planted in the same locality
2. It will grow normally
3. It may not survive because of change in its microclimate
4. It grows very well because the plant gets more sunlight

Answer: (c)

A well growing herbaceous plant in forest receives light of less intensity, duration and quality. But when it is transplanted in a park outside its natural habitat, its light supply will be uninterrupted which will be harmful for it.

So, due to change in its microclimate, it may not survive.

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Q9. Large Woody Vines are more commonly found in

1. Temperate forests
2. Tropical rainforests
3. Mangroves
4. Alpine forests

Answer: (b)

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Q10. It is much easier for a small animal to run uphill than for a large animal, because

1. the efficiency of muscles in large animals is less than in the small animals
2. small animals have a lower $O_2$ requirement
3. it is easier to carry a small body weight
4. smaller animals have a higher metabolic rate.

Answer: (a)

The small animals have smaller surface area to body volume ratio. They have higher metabolic rates than larger animals. Therefore, it is much easier for small animals to move uphill than large animals.

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Q11. Which one of the following population interactions is widely used in medical science for the production of antibiotics?

1. Commensalism
2. Parasitism
3. Mutualism
4. Amensalism

Answer: (d)

Amensalism is a relationship between organisms of different species in which an organism does not allow other organism to grow or live near it. Inhibition is achieved through the secretion of chemicals called allochemics. Antibiotics are a kind of allochemics produced by some microbes which in small concentration can kill or retard growth of harmful microbes without adversely affecting the host.

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Q12. Choose the correct statement.

1. Animals restricted to a narrow range of salinity are euryhaline
2. Among the red, green and brown algae, the red algae are found in the deepest ocean
3. Every winter, the famous Keoladeo National Park (Odisha) hosts thousands of migratory birds
4. The mammals of colder climates generally have longer extremities to minimise heat loss

Answer: (b)

This statement is correct. Rest of the statements are incorrect and can be corrected as

• Animals having a wide range of salinity are euryhaline.
• Every winter the famous Keoladeo National Park (Bharatpur) in Rajasthan, hosts thousands of migratory birds.
• The mammals of colder climates generally have shorter extremities to minimise heat loss.

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Q13. The figure given below is a diagrammatic representation of response of organisms to abiotic factors. What do (A), (B) and (C) represent respectively?

1. A: Partial regulators, B: Conformers, C: Regulators
2. A: Conformers, B: Partial regulators C: Regulators
3. A: Regulators, B: Partial regulators, C: Conformers
4. A: Conformers, B: Regulators, C: Partial regulators

Answer: (d)

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Q14. A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is

1. 05
2. 10
3. zero
4. 15

Answer: (c)

Natality and immigration positively contribute to the population growth while mortality and emigration are negative factors. In the given question,

The net increase in population is natality + immigration = 250 + 20 = 270

The net decrease in population is mortality + emigration = 240 + 30 = 270

Thus, net increase in population = 270 – 270 = 0

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Q15. At which latitude, heat gain through insulation approximately equals heat loss through terrestrial radiation ?

1. 66° North and South
2. 40° North and South
3. 22 $1/2$° North and South
4. 42 $1/2$° North and South

Answer: (b)

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Q16. Consider the following statements (A to D) each with one or two blanks.

1. Bears go into __(a)__ during winter to __(b)__ cold weather.
2. A conical age pyramid with a broad base represents __(c)__ human population.
3. A wasp pollinating a fig flower is an example of __(d)__.
4. An area with high levels of species richness is known as __(e)__

Which one of the following options, gives the correct fill ups for the respective blank numbers from (a) to (e) in the statements?

1. (a) aestivation, (b) escape, (c) stable, (d) mutualism
2. (c) stable (d) commensalism, (e) marsh
3. (c) expanding, (d) commensalism, (e) biodiversity park
4. (a) hibernation, (b) escape, (c) expanding (e) hot spot

Answer: (d)

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Q17. Many tribes living in the high altitude of Himalayas have a

1. lower WBC count than people living in the plains.
2. higher WBC count than people living in the plains.
3. higher RBC count than people living in the plains.
4. lower RBC count than people living in the plains.

Answer: (c)

At the high altitudes, the atmospheric pressure of $O_{2}$ will be too low so the solubility of oxygen in the blood will be very less hence the oxygen carried by each RBC will be too less. But to fulfil the oxygen requirement of the body blood has to carry more oxygen to the body tissue and this is done by the increased number of RBCs.

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Q18. The attributes of population but not of the individual are

1. death rate
2. birth rate
3. sex ratio
4. All of these

Answer: (d)

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Q19. What is the best pH of the soil for cultivation of plants?

1. 3.4-5.4
2. 4.5-8.5
3. 6.5-7.5
4. 5.5-6.5

Answer: (d)

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Q20. Match the following

1. A-IV; B-III; C-II; D-I
2. A-III; B-IV; C-I; D-II
3. A-I; B-III; C-II; D-IV
4. A-III; B-IV; C-II; D-I

Answer: (b)

Predation is a relation between two organisms in which one organism captures and feeds on other. Commensalism is a relation between two organisms in which one benefits and the other neither derives benefit nor harms.

Parasitism is a relation between organisms in which one lives as a parasite on another and harms the host. Competition is process in which the fitness and survival ability of one species is significantly lower in the presence of another species.

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Q21. Just as a person moving from Delhi to Shimla to escape the heat for the duration of hot summer, thousands of migratory birds from Siberia and other extremely cold northern regions move to

1. Western Ghat
2. Corbett National Park
3. Meghalaya
4. Keoladeo National Park

Answer: (d)

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Q22. If the mean and the median pertaining to a certain character of a population are of the same value, the following is most likely to occur

1. a bi-modal distribution
2. a skewed curve
3. a T-shaped curve
4. a normal distribution

Answer: (d)

If the mean and the median pertaining to a certain character of a population are of the same value, a normal distribution is most likely to occur.

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Q23. Connell’s elegant field experiments are related to barnacle, in which superior barnacle Balanus dominates the intertidal area, and excludes the smaller barnacle Chathamalus from that zone. This phenomenon is called

1. competitive release
2. competitive exclusion principle
3. interspecific competition
4. none of the above

Answer: (a)

Competitive release is the growth of the species range when a competitor for its niche is eliminated. It usually occurs when one of two species competing for the same resource disappears, thereby allowing the remaining competitor to utilize the resource more fully than it could in the presence of the first species.

Joseph Connell's (1961) demonstrates competitive release for study of competition for space between the barnacle species Balanus and Chathamalus in the intertidal zone on the rocky Scottish coast.

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Q24. Assertion: Very small animals are rarely found in Polar regions.

Reason: Small animals have a larger surface area relative to their volume; they tend to lose body heat very fast when it is cold outside.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (b)

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Q25. Desert regions are characterized by _________ centimetres of rainfall per year.

1. less than 15
2. less than 5
3. less than 25
4. over 50

Answer: (c)

Deserts have less than 25 centimetres of rainfall per year.

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Q26. Biosphere is

1. Composed of the plants present in the soil
2. A component in the ecosystem
3. Life in the outer space
4. Composed of all living organisms present on earth which interacts with the physical environment.

Answer: (d)

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Q27. Which of the following would necessarily decrease the density of a population in a given habitat?

1. Immigration > emigration
2. Natality > mortality
3. Mortality and emigration
4. Natality and immigration

Answer: (c)

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Q28. The relationship between hermit crab and sea anemone is

1. mutualism
2. symbiosis
3. parasitism
4. commensalism

Answer: (d)

Commensalism is a relationship between organism and its host in which the host neither benefits nor suffers from the association, e.g., hermit crab and sea anemone.

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Q29. Identify the incorrect statement

1. Thermoregulation energetically least expensive process for many organisms like shrews and hummingbirds.
2. 99% animals and nearly all plants cannot maintain their constant internal environment.
3. During the course of evolution, the costs and heights of maintaining a constant internal environment are discarded.
4. In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient water osmotic concentration.

1. (iii) and (iv)
2. (i) and (ii)
3. (i) and (iii)
4. (ii) and (iii)

Answer: (c)

Thermoregulation is energetically expensive for many organisms particularly true for small animals like shrews and hummingbirds. During the course of evolution, the costs benefits of maintaining a constant internal environment are taken into consideration.

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Q30. What does the shape of the given age pyramids(a to c) reflect about the growth status of populations ?

Answer: (c)

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Q31. Biosphere is

1. composed of the plants present in the soil
2. a component in the ecosystem
3. life in the outer space
4. composed of all living organisms present on earth which interact with the physical environment

Answer: (d)

Biosphere is composed of all living organisms present on earth which interact with their physical environment. The other three options, represents only a part of ecosystem.

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Q32. In exponential growth, the increase or decrease in population size during a unit period is

1. (b + d) – N
2. (B + I ) – (D + E)
3. N × (b – d)
4. r + N

Answer: (c)

In exponential growth, the increase or decrease in population size during a unit period is N × (b – d).

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Q33. Identify A, B, C and D in this figure.

1. A: Natality (B), B: immigration (I), C: Mortality (D), D: Emigration (E)
2. A: Immigration (I), B: Emigration (E), C: Natality (B), D: Mortality (D)
3. A: Mortality (D), B: Emigration (E), C: Natality (B), D: Immigration (I)
4. A: Mortality (D), B: Natality (B), C: Emigration (E), D: Immigration (I)

Answer: (b)

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Q34. The age pyramid with broad base indicates

1. low percentage of young individuals
2. high percentage of old individuals
3. a stable population
4. high percentage of young individuals.

Answer: (d)

Age pyramid is a graphic representation of abundance of individuals of different age groups with pre-reproductive individuals at the base, reproductive individuals in the middle and post-reproductive individuals at the top.

Triangular age pyramid has high proportion of pre- reproductive individuals, moderate number of reproductive individuals and fewer post- reproductive individuals. It represents young or rapidly growing population. In bell-shaped age pyramid, the number of pre-reproductive and reproductive individuals is almost equal. Post - reproductive individuals are comparatively fewer.

It represents stable or stationary population where growth rate is nearly zero. In urn-shaped age pyramid, the number of reproductive individuals is higher than the number of pre-reproductive individuals. It represents declining or diminishing population.

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Q35. The foraging, reproductive and migratory activities of the organisms are primarily dependent upon

1. Temperature
2. Light
3. Water
4. Soil

Answer: (b)

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Q36. Effect of parasite on host

1. Reduce growth and reproduction
2. Reduce survival
3. Reduce its population density
4. All of these

Answer: (d)

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Q37. More than 70% of world's freshwater is contained in

1. Antarctica
2. greenland
3. glaciers and mountains
4. polar ice

Answer: (d)

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Q38. Which of the following is correct?

1. 'Brood parasitism' is absent in cuckoo
2. Parasites do not tend to coevolve with the host
3. In general, herbivores and plants appear to be more adversely affected by competition than carnivores
4. The life cycle of parasites is often very simple involving one intermediate host or vector

Answer: (c)

This statement is correct. Rest of the statements are incorrect and can be corrected as

• Parasites tend to coevolve with the host.
• Brood parasitism is present in cuckoo.
• The life cycle of parasites is often very complex involving one or more intermediate hosts or vectors.

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Q39. Fresh water animals cannot live for long in sea water because they would face problems of

1. Purity
2. Vapour pressure
3. Osmotic
4. Thermal change

Answer: (c)

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Q40. It is much easier for a small animal to run uphill than for animal, because:

1. Smaller animals have a higher metabolic rate
2. It is easier to carry a small body weight
3. Small animals have a lower $O_2$ requirement
4. The efficiency of muscles in large animals is less than in the small animals

Answer: (a)

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Q41. Which of the following is correct?

1. Archaebacteria can flourish in hot springs and deep sea hydrothermal vents where temperature is above 100°C
2. Antarctic fishes can survive below O°C as these have antifreeze solutes in their body
3. Desert lizard lacks the physiological ability to cope with extreme temperature, but manage the body temperature by behavioural means
4. All of the above

Answer: (d)

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Q42. In desert grasslands, which type of animals are relatively more abundant?

1. Diurnal
2. Aquatic
3. Arboreal
4. Fossorial

Answer: (d)

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Q43. Which of the following forest plants controls the light conditions at the ground?

1. Shrubs
2. Lianas and climbers
3. Tall trees
4. Herbs

Answer: (c)

Light is an important abiotic component that controls a number of life processes in organism in a forest ecosystem. Its intensity, duration and quality at ground is controlled by tall trees, that have higher productivity than shrubs and herbs growing underneath.

Lianas and climber are woody vines which make commensalism associated with tall trees. Herbs and shrubs occupy lower strata of forest.

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Q44. ....A.... parasite have simple life cycle and ....B.... parasite have complex life cycle.

1. A– Endo, B– brood
2. A– Ecto, B– endo
3. A– Brood, B– endo
4. A– Brood, B– ecto

Answer: (b)

Ectoparasites have a simple life cycle because they live on the host organism and derive nutrition from them. Endoparasites have complex life cycle because they live inside the host. This complex life cycle is because of their extreme specialisation to survive inside the host organism.

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Q45. In which of the following interactions both partners are adversely affected?

1. Predation
2. Competition
3. Parasitism
4. Mutualism

Answer: (b)

Competition is the negative interaction that occurs among organisms whenever two or more organisms require the same limited reasource. Thus, it adversely affects both the partners involved.

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Q46. Annual migration does not occur in the case of

1. arctic tern
2. siberian crane
3. salmon
4. salamander

Answer: (d)

Migration is the seasonal movement of complete populations of animals to a more favourable environment. It is common in mammals (e.g., porpoises), fish (e.g., eels and salmon) and some insects but is most marked in birds. The arctic tern, for example, migrates annually from its breeding ground in the Arctic circle to the Antarctic. Salmon usually migrate from marine to fresh water to spawn.

The siberian crane, breeds in arctic Russia in Yakutia and Western Siberia. It is a long distant migrant. Salamander is an amphibian with slender body, short legs and long tail. Outside the breeding season they are seldom seen as they spend most of their time underground.

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Q47. Which statement does not reflect a reason why grasses predominate in savannas ?

1. Grasses grow well in fine, sandy soils.
2. There are few native herbivores in this biome.
3. The above ground portions of grass plants die during dry seasons.
4. The deep roots of the grasses can survive many months of drought.

Answer: (b)

Grasslands are typically maintained by grazing herbivores and by periodic fires. Overgrazing, such as may occur if agricultural livestock are introduced, which can lead to destruction of the grassland.

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Q48. When does the growth rate of a population following the logistic model equal zero? The logistic model is given as dN/dt = rN(l-N/K)

1. when N/K equals zero
2. when N nears the carrying capacity of the habitat
3. when death rate is greater than birth rate
4. when N/K is exactly one

Answer: (d)

Growth rate of a population following logistic model equals zero, when N/K is exactly one. In logistic growth model, population growth equation is described as

${dN}/{dt} = rN ({K - N}/K)$

Thus when, $N/K$ = 1 then ${K - N}/K$ = 0

${dN}/{dt}$ = 0

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Q49. To avoid summer-related problems such as heat and desiccation fish undergoes

1. diapause
2. hibernation
3. aestivation
4. none of these

Answer: (c)

Aestivation is the cessation or slowing of metabolic activity during the summer period to avoid problems of heat and desiccation etc.

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Q50. Ratio of natality and mortality of a population is expressed in percentage as

1. Growth rate
2. Vital index
3. Survival rate
4. Biotic potential

Answer: (b)

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Q51. Carrying capacity K means __________

1. Nature's limit for supporting maximum growth of a species.
2. Organism's capability of maximum reproduction.
3. Nature's limit for supporting maximum number of species.
4. Organism's capability to withstand environmental odds.

Answer: (a)

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Q52. In commensalism –

1. Population of commensal may increase while that of host remains unaffected
2. Population of commensal and host remains unaffected
3. Population of both commensal and host increases
4. Population of commensal increases while the populationof host gradually decreases

Answer: (a)

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Q53. Which of the following is a partial root parasite?

1. Mistletoe
2. Sandal wood
3. Orobanche
4. Ganoderma

Answer: (b)

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Q54. Consider the following statements about regulation in humans.

1. In summer, we sweat profusely causing evaporative cooling brings down the body temperature.
2. In winters, we shiver which is an exercise that produces heat and raises the body temperature.

Choose the correct option.

1. Statement II is true, but I is false
2. Statement I is true, but II is false
3. Both statements are true
4. Both statements are false

Answer: (c)

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Q55. Autecology is the

1. relation of an individual to its environment
2. relation of a population to its environment
3. relation of a community to its environment
4. relation of a biome to its environment

Answer: (a)

The study of relationship of an individual is called autecology. So, the relation of a population or community to its environment is called synecology and the rest options are irrelevant.

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Q56. Plants such as Prosopis, Acacia and Capparis represent examples of tropical

1. deciduous forests
2. grasslands
3. evergreen forests
4. thorn forests

Answer: (d)

Tropical shrubs or thorn forests are found in places where moisture conditions are intermediate between desert and savanna on one hand and seasonal or rainforests on the other hand. Acacia and Prosopis are non-succulent perennial plants and Capparis is a xerophytic shrub.

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Q57. Which of the following is correct for r-selected species?

1. Large number of progeny with large size
2. Large number of progeny with small size
3. Small number of progeny with small size
4. Small number of progeny with large size

Answer: (b)

r-selected species have the ability to produce a large number of progeny (offspring) with a small body size. The population growth of these species is a function of biotic potential.

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Q58. Which one of the following organisms reproduces sexually only once in its lifetime?

1. Mango
2. Banana plant
3. Tomato
4. Eucalyptus

Answer: (b)

Those plants which flower once in their life are monocarpic plants e.g., all annuals (wheat, rice),biennials like carrot and radish, perennial like bamboo. Banana is a monocarpic plant, so reproduces sexually once in its lifetime. Rest of the options are incorrect.

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Q59. Every winter the famous .....A..... (Bharatpur) in Rajasthan host thousands of migratory birds coming from .....B..... and other extremely cold .....C..... regions. Fill in the blanks A, B and C.

1. A–Keolado National Park, B–Mexico, C–Eastern
2. A–Keolado National Park, B–America, C–West
3. A–Keolado National Park, B–Siberia, C–Northern
4. A–Keolado National Park, B–Siberia, C–Southern

Answer: (c)

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Q60. Consider the following statements (A) – (D) each with one or two blanks.

1. Lichens represent an intimate (i) relationship between a fungus and (ii) .
2. The (iii) are associations between fungi and the roots of higher plants.
3. Plants need the help of (iv) for pollinating their flowers and dispersing their seeds.
4. The (v) pollinates the fig inflorescence while searching for suitable egg-laying sites.

Which one of the following options, gives the correct fill ups for the respective blank numbers from (i) - (v) in the statements?

1. (i) Mutualistic; (ii) - Cyanobacteria; (iii) - Mycorrhizae; (iv) - Animals; (v) Wasp
2. (i) Parasitic; (ii) - Cyanobacteria; (iii) - Mycorrhizae; (iv) - Wind; (v) - Bee
3. (i) Parasitic; (ii) - Cyanobacteria; (iii) - Mycorrhizae; (iv) - Insect; (v) Bumblebees
4. (i) Mutualistic; (ii) - Cyanobacteria; (iii) - Lichen; (iv) - Wind; (v) Wasp

Answer: (a)

A: Lichen represents an intimate mutualistic (i) relationship between a fungus and cyanobacteria (ii).

B: The mycorrhizae (iii) are the associations between fungi and roots of higher plants.

C: Plants needs the help of animals (iv) for pollinating their flowers and dispersing their seeds.

D: The wasp (v) pollinates the fig inflorescence while searching for suitable egg laying sites.

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Q61. The age structure of a population influences population growth because

1. different age groups have different reproductive capabilities.
2. younger females have more offsprings than do older females.
3. the more individuals that are immature the slower the population will grow.
4. a shorter generation time results in slower population growth.

Answer: (a)

Age distribution is important, as it influences both, natality and mortality of the population. From an ecological viewpoint there are three major ecological ages (age groups) in any population. These are pre-reproductive, reproductive and post-reproductive. The relative duration of these age groups in proportion to the life span varies greatly with different organisms.

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Q62. According to the principle of competitive exclusion, two species cannot continue to occupy the same . . .

1. ecological niche.
2. biome.
3. environmental habitat.
4. range.

Answer: (a)

The competitive exclusion principle is the concept that when the populations of two species compete for the same limited resources, one population will use there sources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other species.

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Q63. The below diagram shows some insects laying eggs in the fruit. Find out the insects from the following.

1. Female anopheles
2. Wasp
3. Culex
4. Honeybee

Answer: (b)

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Q64. The two basic processes which contribute to a increase in population density are

1. natality and immigration
2. mortality and immigration
3. mortality and emigration
4. mortality and emigration

Answer: (a)

Natality and immigration are the two basic process which contribute to an increase in population density. Natality is the proportion of births to the total population in a place in a given time. Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.

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Q65. In which one of the following habitats does the diurnal temperature of soil surface vary most?

1. Shrub land
2. Desert
3. Forest
4. Grassland

Answer: (b)

Deserts are places where the diurnal temperatures vary greatly. It is extremely hot during the day time and very cold at night. This change in temperature also affects the temperature condition of the soil.

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Q66. Tiger census in our national parks and tiger reserves is done by counting

1. Tiger pug marks
2. Tiger cubs
3. Tiger faecal pellets
4. Both (a) and (c)

Answer: (d)

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Q67. Assertion (A): Plants need the help of insects and animals for pollinating their flowers and dispersing their seeds.

Reason (R): Plants offer rewards in the form of pollen and nectar for pollinators and juicy and nutritious fruits for seed dispersers.

1. If both A and R are true, but R is not the correct explanation of A
2. If both A and R are true and R is the correct explanation of A
3. If A is true, but R is false
4. If A is false, but R is true

Answer: (a)

Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion. The correct explanation is as follows

Plants need the help of insects and animals for pollinating their flowers and dispersing their seeds because plants are immobile and require a medium to transfer their pollen to enable reproduction.

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Q68. Keystone species in an ecosystem are those

1. that are most frequent
2. present in maximum number
3. attaining a large biomass
4. contributing to ecosystem properties

Answer: (d)

The keystone species in an ecosystem are those who are the main contributors to the ecosystem.

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Q69. How acclimatization occurs in case of altitude sickness?

1. Increased RBC production
2. Decrease RBC production
3. Increased rate of breathing
4. Both (a) and (c)

Answer: (d)

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Q70. Assertion: Parasite may reduce population density of its host.

Reason: Parasite may reduce survival growth and reproduction of host.

1. If both the assertion and reason are true but the reason is not a correct explanation of the assertion.
2. If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
3. If the assertion is true but the reason is false.
4. If both the assertion and reason are false.

Answer: (b)

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Q71. The logistic population growth is expressed by the equation

1. ${dN}/{dt} = rN({K - N}/K)$
2. ${dN}/{dt} = Nr({K - N}/K)$
3. ${dN}/{dt}$ = rN
4. ${dN}/{dt} = rN ({N - K}/N)$

Answer: (a)

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Q72. Match the following columns.

Codes A B C

1. 2 1 3
2. 3 1 2
3. 3 2 1
4. 2 3 1

Answer: (d)

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Q73. Lichens are the associations of

1. Algae and bacterium
2. Bacteria and fungus
3. Fungus and algae
4. Fungus and virus

Answer: (c)

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Q74. Assertion: In sigmoid growth curve, population finally stabilizes itself.

Reason: Finally, the death rate increases than the birth rate.

1. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
2. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
3. If Assertion is true but Reason is false.
4. If both Assertion and Reason are false.

Answer: (c)

In sigmoid growth curve, finally, growth rate becomes stable because mortality and natality rates become equal to each other and finally the population shows zero growth rate as birth rate equals death rate.

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Q75. Pneumatophores occur in

1. halophytes
2. carnivorous plants
3. free-floating hydrophytes
4. submerged hydrophytes

Answer: (a)

Pneumatophores are breathing or respiratory roots which are found in plants growing in mangroves or water logged soil or saline swamps. Such plants are called halophytes.

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Q76. Explosive growth in human population size can be attributed largely to . . .

1. proliferation of fast-food outlets, leading to easier access to nutrients.
2. declining death rates due to improved medical care.
3. increasing birth rates due to better health and fertility.
4. declining death rates due to declining incidence of war.

Answer: (b)

Human death rates have decreased due to declining infant mortality that has resulted from improved nutrition, medical advances, and better sanitation.

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Q77. Artificial selection to obtain cows yielding higher milk output represents :

1. Disruptive as it splits the population into two, one yielding higher output and the other lower output
2. Directional as it pushes the mean of the character in one direction
3. Stabilizing followed by disruptive as it stabilizes the population to produce higher yielding cows
4. Stabilizing selection as it stabilizes this character in the population

Answer: (b)

Artificial selection to obtain cow yielding higher milk output will shift the peak to one direction, so this represent an example of Directional selection. In stabilizing selection, the organisms with the mean value of the trait are selected. In disruptive selection, both extremes get selected.

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Q78. People who have migrated from the planes to an area adjoining Rohtang Pass about six months back

1. Are not physically fit to play games like football.
2. Have more RBCs and their haemoglobin has a lower binding affinity to $O_2$ .
3. Suffer from altitude sickness with symptoms like nausea, fatigue, etc.
4. Have the usual RBC count but then haemoglobin has very high binding affinity to $O_2$.

Answer: (b)

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Q79. Benthoic animals are those, which

1. float on the sea surface
2. are submerged in area
3. are deep dweller in sea
4. are floating (free) organisms.

Answer: (c)

Benthoic organisms are attached or rest on the bottom sediments. Benthic animal may be divided into filter feeders, e.g., clams and deposit feeders e.g., snails.

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Q80. Leaves become modified into spines in

1. Pea
2. Opuntia
3. Onion
4. Skin cotton

Answer: (b)

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Q81. The age of pyramid with broad base indicates

1. Low percentage of young individuals
2. High percentage of young individuals
3. High percentage of old individuals
4. Low percentage of old individuals

Answer: (b)

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Q82. Altitude sickness occurs at high mountains. This sickness have symptoms like

1. fatigue
2. nausea
3. heart palpitations
4. All of these

Answer: (d)

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Q83. Diapause is

1. Stage of suspended development seen in unfavourable conditions in many zooplankton species in lakes and ponds.
2. Adaptation to terrestrial life.
3. Method of migration from stressful habitat to a more hospitable area.
4. It is a type of symbiosis.

Answer: (a)

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Q84. Major biomes of India include

1. Tropical rainforest
2. Alpine region
3. Deciduous forest
4. Desert
5. Himalayan region
6. Sea coast.

Choose the correct combination for given question.

1. I, II, III and IV
2. I, III, IV and V
3. II, III, IV and VI
4. I, III, IV and VI

Answer: (d)

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Q85. Presence of plants arranged into well defined vertical layers depending on their height can be seen best in

1. tropical rainforest
2. temperate forest
3. grassland
4. tropical savannah

Answer: (a)

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Q86. The figure given below is a diagrammatic representation of response of organisms to abiotic factors. What do A, B and C represent respectively?

1. A: Regulator, B: Partial, C: Conformer regulator
2. A: Conformer, B: Regulator, C: Partial regulator
3. A: Partial, B: Regulator, C: Conformer regulator
4. A: Regulator, B: Conformer, C: Partial regulator

Answer: (d)

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Q87. What is the best pH of soil for cultivation of plants ?

1. 6.5 – 7.5
2. 3.4 – 5.4
3. 4.5 – 8.5
4. 5.6 – 6.5

Answer: (a)

The best pH of soil for cultivation of plants is 6.5 – 7.5.

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Q88. Two different species cannot live for long duration in the same niche or habitat. This law is

1. Gause's hypothesis
2. Allen's law
3. Dollo's rule
4. Weisman's theory.

Answer: (a)

Interspecific competition is rivalry amongst members of different species. The severity of competition depends upon similarity in the requirement of food and shelter. Every type of organism has a particular niche, no two organisms can live in same niche. One of the two is eliminated. This phenomenon is called Gause hypothesis of competitive exclusion.

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Q89. Eutrophication is often seen in

1. Deserts
2. Ocean
3. Fresh water lakes
4. Mountains

Answer: (c)

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Q90. Which is not a part of atmosphere?

1. Temperature
2. Light
3. Edaphic factor
4. Precipitation

Answer: (c)

Because edaphic factors affects through soil and rest are the climatic factors.

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Q91. Just as a person moving from Delhi to Shimla to escape the heat for the duration of hot summer, thousands of migratory birds from Siberia and other extremely cold northern regions move to

1. Meghalaya
2. Western Ghat
3. Corbett National Park
4. Keolado National Park

Answer: (d)

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Q92. Ecological niche is

1. an ecologically adapted zone
2. the surface area of the ocean
3. the physical position and functional role of a species within the community
4. formed of all plants and animals living at the bottom of a lake

Answer: (c)

The specific place of habitat occupied by individual of a species is ecological niche. It in turn is determined by factors such as by the range of tolerance. i.e., the physical position and functional role of a species within the community, etc. Rest of the options are not correct.

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Q93. Select the correct option from the statements given above.

1. Populations evolve to maximisetheir reproductive fitness, also called Darwinian fitness (higherr value), in the habitat in which they live.
2. The population growth rate r is inversely related to generation time.
3. The housefly, which has a short lifespan and produces a large number of eggs, could be considered as a 'K' selected species.
4. Under a particular set of selection pressures, organisms evolve towards the most efficient reproductive strategies.
5. Life history traits of organisms have evolved in relation to the constraints imposed by biotic and abiotic factors in their habitat.

1. I, III and IV
2. I, II and III
3. III, IV and V
4. All except III

Answer: (d)

Statements I, II, IV, and V are correct. Statement III is incorrect and can be corrected as The housefly, which has a short lifespan and produces a large number of eggs could be considered as 'r' selected species.

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Q94. What percentage of animals on this earth are regulators and conformers, respectively?

1. 7% & 93%
2. 2% & 98%
3. 4% & 96%
4. 1% & 99%

Answer: (d)

About 99% of animals and nearly all plants do not have a mechanism to maintain a constant internal body environment and are called conformers as their body temperature changes with the surrounding temperature. Thus, the rest, i.e. only 1% of them are regulators.

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Q95. Assertion (A): The prickly pear cactus introduced into Australia in early 1920s caused havoc by spreading rapidly into millions of hectares of rangeland.

Reason (R): When certain exotic species are introduced into a geographical area, they become invasive and start spreading first because the invaded land does not have its natural predators.

1. If both A and R are true, but R is not the correct explanation of A
2. If both A and R are true and R is the correct explanation of A
3. If A is true, but R is false
4. If A is false, but R is true

Answer: (b)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

When certain exotic species are introduced into a geographical area, they become invasive and start spreading rapidly due to the absence of their natural predators.

Hence, when prickly pear cactus were introduced into Australia in the early 1920s, these plants caused havoc by spreading rapidly into millions of hectares of range land.

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Q96. Assertion: Cold blooded animals do not have fat layer.

Reason: Cold blooded animals use their fat for metabolic process during hibernation.

1. If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
2. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
3. If Assertion is true but Reason is false.
4. If both Assertion and Reason are false.

Answer: (b)

Cold blooded organisms utilize their stored food at the time of hibernation and aestivation.

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Q97. Pedology is the study of –

1. Rocks
2. Locomotion of animals
3. Soil
4. Reproduction

Answer: (c)

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Q98. Aquatic mammals in polar seas have a thick layer of fat known as __________

1. Flubber
2. Blubber
3. Rubber
4. Stubber

Answer: (b)

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Q99. The organisms through natural selection have evolved __________ to optimize its survival and reproduction in its habitat.

1. Adaptations
2. Camouflage
3. Specialized Physiology
4. Higher reproduction rate

Answer: (a)

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Q100. Deserts, rainforests, tundra, etc. are example of

1. biome
2. community
3. ecosystem
4. population

Answer: (a)

A biome is a large regional unit characterized by a major vegetation type and associated fauna found in a specific climatic zone some examples of terrestrial biomes are desert, temperate deciduous forest, tropical rain forest, etc.

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